bwoodry

When I turn the Ignition key all the way over just before actuating the starter I hear a clunk , clunk noise from the passenger side area. This noise happpens each time I turn the Key. Sounds like a smal gate or door closing,. Has anyone else heard this andif so have you figured out the cause?

Tks

Bob

Youcef

Sure its not from the engine bay with the resonance valve testing itself.

garrett376

If you have a C4, it's your differential locks (2 of them) going though their test operation.

bwoodry

OK So either the Diff Locks or the Resonance valve.
I will check both.

This site is fantastic!!!

garrett376

I find the resonance valve is pretty hard to hear, unless your head is in the engine compartment - and the sound is behind you vs in the "passenger seat". One easy way to see if it's the same noise (given you have a C4): while the engine is idling, turn on the Traction Control Program (lock the differential locks) by turning the switch on the center console (in front of the gearshift lever), then turn it off - when it turns off and the lock pressure is released, I bet the sound you hear will be the same as what you've been hearing all along. If not, then you might just have a really loud resonance valve!!!